Problem: Solve for $x$ and $y$ using substitution. ${3x+y = 3}$ ${y = -2x+1}$
Explanation: Since $y$ has already been solved for, substitute $-2x+1$ for $y$ in the first equation. ${3x + }{(-2x+1)}{= 3}$ Simplify and solve for $x$ $3x-2x + 1 = 3$ $x+1 = 3$ $x+1{-1} = 3{-1}$ ${x = 2}$ Now that you know ${x = 2}$ , plug it back into $\thinspace {y = -2x+1}\thinspace$ to find $y$ ${y = -2}{(2)}{ + 1}$ $y = -4 + 1$ $y = -3$ You can also plug ${x = 2}$ into $\thinspace {3x+y = 3}\thinspace$ and get the same answer for $y$ : ${3}{(2)}{ + y = 3}$ ${y = -3}$